Truck tires, for example light and medium duty truck tires, are expected to be able to carry heaver workloads than passenger tires. Their treads are expected to experience greater stresses for their rubber composition and greater internal heat generation and correspondingly greater internal temperature built up as the tire is being worked as well as to experience greater rates of treadwear.
Truck tire treads generally rely upon particulate reinforcing filler in a form of rubber reinforcing carbon black for their rubber reinforcement.
While various advantages have been observed for using particulate reinforcing filler in a form of precipitated silica or a combination of reinforcing carbon black and precipitated silica filler reinforcement, together with a coupling agent for the silica, for passenger tire tread rubber compositions, such combination of reinforcing fillers which include silica are typically not used for truck tires.
Accordingly, a challenge is presented for providing a truck tire tread of a rubber composition which contains both carbon black and precipitated silica reinforcement.
For this invention, epoxidized elastomers are contemplated, namely epoxidized natural rubber (epoxidized natural cis 1,4-polyisoprene rubber), epoxidized polybutadiene rubber and epoxidized styrene/butadiene rubber.
For this invention, an epoxidized natural rubber is evaluated for use as a compatabilizer for compatabilizing amorphous synthetic silica (precipitated silica) with diene-based elastomers comprised of cis 1,4-polyisoprene rubber and cis 1,4-polybutadiene rubber.
Historically, epoxidized natural rubber has been used with various diene-based elastomers in various rubber compositions. For example, see U.S. Pat. Nos. 5,396,940, 5,462,979, 5,475,051, 5,488,077, 5,504,140, 5,552,490, 5,569,690, 5,714,533, 5,736,593, 6,220,323, 6,220,323, 6,220,326, 6,482,884, 6,593,418, 6,737,466, 6,759,464, 6,845,797, 7,122,586, 7,152,642, 7,214,731, 7,371,791, 7,375,156 and 7,709,560.
In the description of this invention, the term “phr,” where used, and according to conventional practice, refers to “parts of a respective material per 100 parts by weight of rubber or elastomer”.
In the description of this invention, the terms “rubber” and “elastomer,” if used herein, may be used interchangeably, unless otherwise prescribed. The terms “rubber composition,” “compounded rubber” and “rubber compound,” if used herein, are used interchangeably to refer to “rubber which has been blended or mixed with various ingredients and materials” and such terms are well known to those having skill in the rubber mixing or rubber compounding art. The terms “cure” and “vulcanize” may also be used interchangeably unless otherwise noted.